1. Field of the Invention
The present invention relates to a two-dimensional position detecting device for detecting the position of an object which moves in a plane.
2. Description of the Prior Art
A two-dimensional position detecting device including a two-dimensional position sensitive device (two-dimensional position sensor) (PSD) and a light source (LED) which are respectively mounted to one and the other of a stationary member and a movable member so as to face each other in order to detect the position of incident light, which is emitted from the light source to be incident on the two-dimensional position sensor, to thereby detect the position of the movable member relative to the stationary member is known in the art as a position detecting device for detecting the position of a moving object in a plane within a maximum moving range of the order of a few millimeters. This type of position detecting device is disclosed in Japanese unexamined patent publication No. 2001-117129.
However, in a conventional two-dimensional position sensor, the effective length and width (the effective area) of the light receiving surface is only about two millimeters. Therefore, in the conventional detection method using a light source and a two-dimensional position sensor that are arranged so as to face each other, the position of the movable member relative to the stationary member can only be detected within a small operating area which corresponds to the two-dimensional area of the light receiving surface of the two-dimensional position sensor.